RC Trainer Question

Levent has it correct, Yabby. The trainer model is trimmed to glide when engine runs out of fuel ("dead stick") without any radio assistance, as though it was a free flight. So, there is positive incidence (wing front tilted up slightly) and elevator with negative incidence (tilted slightly down). Under power, it is flying faster than a glide, so it has a tendency to climb. To compensate, down thrust (engine pointed down) helps to compensate for this. The torque of the engine on most planes cause it to turn naturally to the left, so right thrust (engine pointed to the right) is used to help the plane fly straight.

The downthrust IMO, doesn't have to fully remove the tendency for the trainer to climb, it just climbs out more slowly.

I'm thinking possibly that you may be targeting your son for such a flying venture?

The trainer you picked out is similar to the more popular Sharkface. There are others. The Q-Tee is another popular trainer. I built Ken Willard's 27" Schoolboy for .020 and 39" Schoolmaster for .049-.10, Sterling 36" Minnie Mambo, Ace 44" Grasshopper. A similar Cricket is available on Outerzone. Also built foamie .049 ARF's. A little more power turns them into real fun flies.

If flown high enough, a plane set up this way tends to straighten itself if one gets into trouble and lets go of the controls. In an ideal world, setting up the plane in this way by making minor adjustments to thrust and glide will have a plane with minimal climb under power and straight glide. But, once the "coarse adjustments" are set, I just use the trim levers to correct powered flight, then control the glide with the sticks. I have never got these adjustments tweaked to perfection, because it is not needed.

Under experienced hands, we call them "sport planes" or "relaxed fliers".

Thank you so very much for the link you posted in response! Knowing you have to build something a certain way is fine. But understanding the reason for it helps out with a lot more. Understanding the reason helps understand how to fly the plane and expect the controls to behave etc. It makes perfect sense when it is explained. But it was not something I would intuitively work out or reason for myself. but when explained in the way the link you posted does, I can certainly understand it. The link provides an excellent description in plain simple terms of which I can readily understand and now I can see why a trainer has more dihedral, downward thrust, wing mounted high etc. I have been reading stuff on the net and I often find a lot of this sort of thing is explained in pure physics and math which I find heavy going to find the answer or reason.

Probably a funny question coming from someone who works for the company that designed and built the SR-71 But we are not all employed as aircraft/aerospace aerodynamic engineers, which is a lucky thing for me.

Greatly appreciated response and link!



Yabby

Just a little trick to keep your orientation with your nose imagine yourself on board the plane the nose of the plane is always in the same place as yours Not just looking at the plane but making a visual connection is To imagining being the plane

Yabby, in the 1980's, I worked in Structural Test Labs at Douglas Aircraft Company in Long Beach, CA. I worked on the software side of testing, also went a few times on wind tunnel tests, operated the data systems and did graphic plots, so didn't really get involved with the aerodynamics side. (In the hangars, our computers did everything from components to whole airframes.)

However, even as a small child, always had a fascination with aircraft flight. Regarding theory, took two fluid dynamics courses, one was undergraduate, another was graduate level but geared towards use of the computer to solve complex fluid equations. (Air is treated as a fluid, just like water.) But, those didn't get into the specifics of aircraft aerodynamics, except briefly on airfoils.

But, regarding aerodynamics, mostly read it from model airplane books regarding such. Interested more in the practical than the theoretical, learned to make do with what others have learned previously. And, interested in more the simpler than the complex.

To me, it is just fascinating to see your own creation take to the sky, whether a kite, glider, rubber powered, free flight, or simple RC. Just to see something moving in flight always fascinated me.

Good luck on your RC build.

GG has already listed several alternate planes that would make good trainers.  I would like to add the Honker (my avatar) by Dave Thornburg.  It is also a slab-sided quick build and is a gentle flyer. Leave the gear off.  Another option is the 1/2A SST.  The plans show a foam wing, but you can easily convert to a built-up wing.

For belly landers, to protect the fuselage bottom, I add a strip of DUCK Heavy Duty clear tape, running from the firewall to just behind where the wheels would be.  This gives some resistance to small rocks and pokes from dried grass stems.

The only downside I see with your choice is that the airfoil is a little thin and that will have a tendency to make the plane a bit faster than other planes -- for me, the slower the better when learning.

andrew wrote:The only downside I see with your choice is that the airfoil is a little thin and that will have a tendency to make the plane a bit faster than other planes -- for me, the slower the better when learning.

Did you download the plan?

I did and had a look. Airfoil is standard modified Clark-Y of half inch height, only appears a touch thinner than others. On the fuselage elevation, what looks like may be a flat plate wing are the resting rails for the wing, to allow the dihedral Vee clear the center of the fuselage where the wing rests.


You mentioned the Honker as another fine trainer.  If you think about it, the Honker, a fine shoulder wing plane of similar proportions uses a thinner Jedelsky wing section, but was a decent robust aircraft. Regarding speed, as the Teeny has a 37" wingspan, should be okay. Our modern radio systems are lighter in weight and as such, the Teeny should do fine speed wise. If one is concerned, can mount the prop backwards to reduce thrust and initial speed on first flights.

The Teeny aircraft IMO would be an ideal candidate for a K-Flex airfoil foam wing.

Yabby,

That is an interesting first plane.  As pointed out above, down and right thrust are normal on trainers.  It seems that the plan you posted has more than the usual amount of down thrust.  I'd imagine because of the slab wing.  I'm sure it would fly.  But I'm not sold on the slab wing.  Although I love slab wing C/L planes, I don't think I would do it with a first RC plane.  The built up wing shown on the plan is better, but still seems rather thin.  For a first plane, you want a floater, and a flat or nearly so wing doesn't float well.  The Honker series use sheet wings, but the sheet is formed into an airfoil shape.  Better.

The Q-Tee suggested is a good plane.  Between the Q-Tee and a Cox E-Z Bee, I taught myself to fly.  But, instead of a Q-Tee for a first plane, love it though I do, I'd suggest the S-Tee (here).  It's the same plane, but without the cabanes.  Cabanes are not hard to make, but they're just one more thing you have to get aligned just right.  For simplicity, you could leave off the turtledeck and windscreen from the S-Tee and it'd be about the same as the plane you posted, just better for a first plane in my opinion.  Of course, another classic plane that I also recommend is the RCM 1/2A Basic Trainer(here).  Easy to build and classic lines that I love.

Another plane that I'd suggest, probably ahead of any of the others for a first plane, is the Papillon(here).  It is a 1/2A motor glider that flies great.  This was actually the first plane that I ever built.  Take a look at it.  A little more work than the one you posted, but maybe a little less than the others suggested.  Again, another of my personal favorites for easy and relaxed flying, as well as a good beginner's plane.  It doesn't have landing gear, like the one you posted.  But it does have a small skid for landing that saves the bottom of the fuselage.  I have an original kit in the box that's been waiting a long time to be built, and I should finally build it for nostalgia.


Sorry, this post strays from your initial question, but since when can I stay on topic?

The Drifter Mark

GallopingGhostler wrote:
Did you download the plan?

Actually, I did download the file before commenting.

The basic wing uses 2 sheets of 1/4 x 3; the Clark Y section shown is for an alternate balsa built-up or for foam construction -- the rib and spar locations on the basic layout are for the optional built-up wing. The rails you mentioned are, I believe, the basic wing and the drawing is incorrect in that F3 would need to either be notched at the top for the center section or moved forward 1/8". Being somewhat lazy, I likely would adjust F3 and let the center section just butt up against it.

Flat plate wings are notoriously draggy, so while a 4% airfoil in this configuration, this model may turn out to be sufficiently slow for a new flyer to stay ahead of it. Most certainly, the construction is simple enough, would be a quick build and easily repaired or replaced.

If I were inclined to build a wing, the Schoolboy wing, scaled to chord and adjusted to span, would be a good candidate. I has about a 12.5% airfoil, is of simple construction, is robust and would be my preference over the optional airfoil on the Teeny plans. I don't think a Jedelsky wing is a good choice for the first time builder -- it's more time consuming, although simple, requires the forward section to be carefully planed down and, for some models, uses tapered stock (now hard to find and pricey).

Foam wings are another option, both the KF and Armin versions, but there is, at least for me, a learning curve, particularly the Armin airfoil, in building a good wing.

andrew wrote:

GallopingGhostler wrote:Did you download the plan?

Actually, I did download the file before commenting.  

The basic wing uses 2 sheets of 1/4 x 3; the Clark Y section shown is for an alternate balsa built-up or for foam construction -- the rib and spar locations on the basic layout are for the optional built-up wing.  The rails you mentioned are, I believe, the basic wing and the drawing is incorrect in that F3 would need to either be notched at the top for the center section or moved forward 1/8".  Being somewhat lazy, I likely would adjust F3 and let the center section just butt up against it.

You are right Andrew, I stand corrected. It wasn't clear in the plans, but after re-examining the article, the photos make it more clear. My 1959 Berkeley Impulse build uses the wing saddles. In a way there is an advantage, as I can trim that saddle to reduce the wing decalage, as I'm making it 3 channel. Originally it was single channel escapement with kick up elevator.

Another simple one, Yabby, if you care to contact a foam wing cutter for a set of Ace R/C style universal half A wings. Those foam wings made easy work of wing construction, but with a decent airfoil.

https://outerzone.co.uk/plan_details.asp?ID=7150


Outerzone #7150: 41in. Cricket by Art Bigelow from June 1990 RCM

Hi All,

Thanks heaps for all of the suggestions and ideas and advice. all of whih comes from experience I dont have, so is greatly valued by me.

My son and I fly half-A CL with Cox 049 engines, both surestart and TD and we do enjoy it. I used to fly CL Combat wings with an Enya 15 when I was in my teens and came bak to flying CL about 4 yrears ago and Im now 61. Im not a very good CL flyer at all, but I still haver fun flying them. We have also been driving RC 049 air Cars that I built and I feel much better using a radio control even though its a car than CL. The coming to me and goinjg away from me has been no problem at all, same for throttle and steering.

Im going to build an RC trainer beause I just want to have a go at it. I had wondered about the slab wing on the plane I was looking at and most of the posts have confirmed to me my concern about that, as I really want a slow, stable, floater, and it very much seems a built up wing with proper aerofyle will make a big difference in that respect. I will look through all of the various models people have suggested and try and sort one out that I think will give me my best chance at flying successfully. For me though, the ease of build is quite important also, and I have been looking on the net to see if I can get a reasonable foam wing in Australia, otherwise I will build one up. I enjoy flying my planes but Im not someone who overly enjoys building them unfortunately.

I build and drive all kinds of things, planes, cars, hovercrafts, boats, because they are all different and I learn lots about different engineering/sciene/physics when I muck around with the different types of models. The link to balsaworkbench was great as the content in there lines up with what everyone I is explaining in their posts here to me. The really good stuff in that site is the stuff on how to trim and setup the plane using the radio but not pwering the engine and basically flying it as a glider. It would seem to me, that regardless of what I build, the steps to try and trim it etc. explained in the balsaworkbench site are absolutely invaluable.

I will spend time looking at all of the suggested models and it seems clear to me that I really should do a built up wing and what will be a floater. Im sure I will get one of the suggested models built and working and my lad and I will have a great time flying it. We dont fly in a club or with others, so it is very simple and just comes down to us having a happy fun time, which we do with all the different type models we use. But I do like the feel of RC!

Thanks very much to everyone for the considered responses and advice. It is genuinely valuable and appreiated advice and lots of things I would never have even known to consider. I reckon Im in with at least half a chance now!



Yabby

Yabby wrote:

I will spend time looking at all of the suggested models and it seems clear to me that I really should do a built up wing and what will be a floater.  Im sure I will get one of the suggested models built and working and my lad and I will have a great time flying it.  
Yabby

Of all the models suggested, I think batjac or The (insert the word of the day) Mark has the best recommendation:  Papillon .  This is essentially a motor glider -- a true floater; it's larger and more easily seen at a distance which will help with orientation; with its size, it will be slower and will respond more slowly to commands, giving you a chance to make corrections if needed; after the engine run, deadstick time should be longer than with some of the other planes.  I think you'll find it to be an excellent "learn on your own" first aircraft.

Yabby wrote:
We dont fly in a club or with others, so it is very simple and just comes down to us having a happy fun time, which we do with all the different type models we use.

Your comment perfectly sums up the essence of family and modeling.  Good on you!

The good thing Yabby when you toss your first trainer into the atmosphere is you already have the experience of your air cars to help with right-left command inputs….That seems to be the tuffest part for new fliers….Especially coming toward you…

The other advantage you have is control input experience from CL…Sometimes just a little correction and other times a lot..

I’m sure with one of the above mentioned trainers you will be successful… When the time finally comes, Keep the plane upwind… If you make a mistake it will blow it back too you instead of away…. Much harder battle to come back from down wind…

Just to add to the confusion. May I recommend the LST 1/2a trainer. Built and flown by many as well.

https://aerofred.com/details.php?image_id=96378#google_vignette

I would post the link to the original, but it is on another RC site and did not want to post it here. But either Google it or message me and I will get you those links should you want. Kind of a miniature Kadet.....

NEW222 wrote:..... May I recommend the LST 1/2a trainer. Built and flown by many as well......

..........I would post the link to the original, but it is on another RC site and did not want to post it here.....

Many of the posters on this forum were also active on the 1/2A forum when RC Universe was popular, consequently, I don't think that any reference to the thread would be either unethical or in violation of forum rules.  The 1/2A LST was designed by Andrew Donatelli (Bipe Flyer) as a tribute to Lynn Sipes, a well liked and enthusiastic modeler --- the LST or Lynn Sipes Trainer was a memoriam to a passed forum member.

We have done the same here for Rusty Knowlton (RknRusty) with the thread Rusty's Memorial Traveling Engines -- Lynn Sipes was Rusty's alter ego on RCU.

The RCU thread, Building and flying the LST 1/2A Trainer has over 215,000 views, so it obviously has something to offer.

I would be inclined to build it as a tail dragger to save a little weight, then leave the gear off during the learning phase -- sometimes landings by new pilots can be less than perfect and the gear can get ripped off.

I also have the files as a full sized tiled PDF and would be glad to send them out to anyone interested.

andrew

This is one that is a bit unusual, but today would be easy to make the wings of corrugated plastic sign material and the fuselage out of poster foamboard.

https://outerzone.co.uk/plan_details.asp?ID=13996
Outerzone Plan# 13996 - Plato by Ernest Houslander from Model Builder June 1983, 30in span





It was originally designed to use single channel or galloping ghost equipment. Interestingly, it was stated as being very stable, easy to fly, easy to take off from the ground. With the modern construction materials should be almost indestructible. I saved a copy to my hard disk as an easy build.

Watching the videos of the scamp and jr falcon, got my interest back on flying a Jr falcon.  Does anyone sell a short kit for the falcon or scamp? The Plato should be one to build now, seems like its election time, signs everywhere!!!

GallopingGhostler wrote:This is one that is a bit unusual, but today would be easy to make the wings of corrugated plastic sign material and the fuselage out of poster foamboard.

It was originally designed to use single channel or galloping ghost equipment. Interestingly, it was stated as being very stable, easy to fly, easy to take off from the ground. With the modern construction materials should be almost indestructible. I saved a copy to my hard disk as an easy build.

now that will definately distract me. You have probably noticed my liking for unusual and odd types of builds But Im going to stay strong on this one and go down the more mainstream path or I will never build an RC plane to crash. but it is a very interesting and tempting design and build. But a Cox 049 powered floater it will be. Ive still got my Combat wing on the bench waiting for its controls and some solarfilm so as that I can fly it. And after all these years its going to be a blast to fly an OS or Enya 15 powered wing again:Thumbs UP:

Yabby

Yabby, the original article had this to state,

Ernest Houslander, Oct. 1960 American Modeler wrote:Plato I was a 24 in saucer, high wing design with the motor mounted above the wing on an extension of the rudder, six inches back from the leading edge. It was underpowered with an .074 diesel, so an .09 was installed. This provided adequate to get it up "there", but it was simply too groovey. It would fight a turn and use up about 250 feet in a circle. I've laid this one aside for future use from my rocking chair.

About this time the Pee Wee .020 motor came out and provided the inspiration for Plato II, an 18 inch saucer. It was a high wing design but this time the engine was mounted in its normal position in the fuselage. The weight, 14 oz. overall, made the wing loading a little high, but it was more nimble than Plato I.

The first two design proved the efficiency and strength of the reflex section. It remained to improve the service-ability and simplify the construction so that it could be built with the minimum amount of time and effort. To achieve this, Plato III was built.

The American Modeler magazine was later to become the US Academy of Aeronautics (AMA)'s Model Aviation Magazine, with continuing editor, the late William W. "Bill" Winter as chief editor. This is why it was a quality publication from the start.

Back to the design, it was interesting that Ernest experimented with a couple iterations at different sizes and layouts until he settled on the 30 inch (760 mm) diameter (wingspan) of the saucer for .15-.25 power then (probably equivalent to .10 - .15 Schneurle power now). I can imagine that although the first iteration was sexier with the engine up above the saucer mounted on top and front of the rudder, location of the thrust line complicated adjustments.

The Plato III would be a good candidate for my Enya .19-VI TV. Interestingly enough for an Enya, it has the same power as the 1970's OS Max .15R/C. (Even though both were later in 1970's, most of the time, Enya outdoes the OS slightly for cross scavenged engines.)

Reading between the lines, (remember, with dual bypass port cylinder, the Pee Wee was in essence a miniature Black Widow. ) I gather that for .049 power, probably a 20" to 22" wingspan would be about right.